1. Field of the Invention
The invention relates to panel fasteners; and, more particularly, to captive panel fasteners suitable for securement to aircraft panels or the like.
2. Description of the Prior Art
In U.S. Pat. No. 3,995,675 to Cosenza, there is described a captive panel fastener assembly wherein a retaining ring with inwardly extending tabs slidably ride along the body of a stud, the tabs entering splines extending lengthwise of the stud. A knurled plug is press-fit into a bore at the nose of the stud after insertion of the stud through a hole in a panel and after placement of the ring on the stud. This retains the ring to the stud and allows a more rigid and closely fitting retaining ring to be used as a captivating means of the stud to the panel. The retaining ring is more resistant to accidental displacement than more flexible retaining rings.
However, the knurl of the plug and its outer diameter must be very precisely manufactured and closely related to the bore diameter into which it is inserted. If it is not so precise, e.g., if it is oversized, the plug can blow up or expand the outer threads of the stud and the stud cannot then mate properly with a receptacle secured to a mating panel. If the plug is undersized, it will fall out and may possibly be sucked up into the engine of the aircraft causing serious damage. If it falls out where sophisticated hardware or electronic equipment is present, it may interfere with the same or cause damage thereto.
Further, the plug in U.S. Pat. No. 3,995,675 has an enlarged shoulder or stop portion which abuts against the area surrounding the bore opening. If this portion is not perfectly concentric with the shaft of the stud, it might interfere with the minor diameter of the thread of the stud and a nut or receptacle would not be able to threadably mate with the stud. Finally, in installing the plug in U.S. Pat. No. 3,995,675, a large axial force is necessary to install the knurled barrel portion all the way into the bore hole.
In my copending application Ser. No. 07/138,513, filed 12/23/87 commonly assigned, I disclose a combination stop ring and hold out spring for a panel fastener assembly. However, it is not necessary that the stop ring be integral with the spring form hold out portion. The plug of U.S. Pat. No. 3,995,675 can be eliminated retaining the advantages of the hold out spring portion by using a conventional stop ring.
In U.S. Pat. Nos. 4,069,855 and 4,119,131 to Petroshanoff, spring members are disclosed entirely contained within the bore of a bolt having a curved portion extending out of a slot through the body of the bolt. There is no firm positive coupling of the springs to the bolt body and these springs can lose their resiliency and fall out of the bolt body upon vibration and the like.
There is thus a need for a captive panel fastener that allows the use of rigid and close fitting retaining rings on bolts or studs which captivate the bolt or stud to a panel without a separate plug or without means that might fall out or interfere with the outer threads of the bolt or stud.